Leon Neal/AFP/Getty Images(JOHANNESBURG) -- Nelson Mandela, the 94-year-old former president of South Africa and anti-apartheid leader, spent a second night in the hospital on Sunday, but officials remain tight-lipped about his condition or the medical tests he is undergoing.

Mandela was admitted on Saturday to 1 Military Hospital in Pretoria.

Presidential spokesman Mac Maharaj said in a statement on Saturday that Mandela had been admitted “to undergo tests.” He said there was no cause for alarm.

On Sunday, Maharaj called on the media and the public to respect the privacy of Mandela and his family.

South African President Jacob Zuma visited Mandela on Sunday and issued a brief statement saying he "found him comfortable, and in good care.”

South African Defence Minister Nosiviwe Mapisa-Nqakula also noted that Mandela was "in good hands" when she visited him on Monday, her spokesperson said. The spokesperson said that the defense minister interacted with Mandela and "is satisfied and can assure us there is no immediate concern."

This is Mandela’s third trip to the hospital since 2011.

Mandela’s last public appearance came in 2010 when he rode on a golf cart at a soccer stadium ahead of the final match of the World Cup. His last meeting with a foreign official came in August when he had lunch with Secretary of State Hillary Clinton.

Mandela was a militant anti-apartheid leader who spent 27 years in prison. After his release in 1990, he led the African National Congress party in negotiations with South Africa’s government that resulted in the end of apartheid and the establishment of democracy. Mandela served as South Africa’s first democratically-elected president from 1994 to 1999.